Line data    Source code

       1             : /* Determine prime number.
       2             :    Copyright (C) 2006 Red Hat, Inc.
       3             :    This file is part of elfutils.
       4             :    Written by Ulrich Drepper <drepper@redhat.com>, 2000.
       5             : 
       6             :    This file is free software; you can redistribute it and/or modify
       7             :    it under the terms of either
       8             : 
       9             :      * the GNU Lesser General Public License as published by the Free
      10             :        Software Foundation; either version 3 of the License, or (at
      11             :        your option) any later version
      12             : 
      13             :    or
      14             : 
      15             :      * the GNU General Public License as published by the Free
      16             :        Software Foundation; either version 2 of the License, or (at
      17             :        your option) any later version
      18             : 
      19             :    or both in parallel, as here.
      20             : 
      21             :    elfutils is distributed in the hope that it will be useful, but
      22             :    WITHOUT ANY WARRANTY; without even the implied warranty of
      23             :    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
      24             :    General Public License for more details.
      25             : 
      26             :    You should have received copies of the GNU General Public License and
      27             :    the GNU Lesser General Public License along with this program.  If
      28             :    not, see <http://www.gnu.org/licenses/>.  */
      29             : 
      30             : #include <stddef.h>
      31             : 
      32             : 
      33             : /* Test whether CANDIDATE is a prime.  */
      34             : static int
      35             : is_prime (size_t candidate)
      36             : {
      37             :   /* No even number and none less than 10 will be passed here.  */
      38       39793 :   size_t divn = 3;
      39       39793 :   size_t sq = divn * divn;
      40             : 
      41      141685 :   while (sq < candidate && candidate % divn != 0)
      42             :     {
      43      101892 :       size_t old_sq = sq;
      44      101892 :       ++divn;
      45      101892 :       sq += 4 * divn;
      46      101892 :       if (sq < old_sq)
      47             :         return 1;
      48      101892 :       ++divn;
      49             :     }
      50             : 
      51       39793 :   return candidate % divn != 0;
      52             : }
      53             : 
      54             : 
      55             : /* We need primes for the table size.  */
      56             : size_t
      57        5704 : next_prime (size_t seed)
      58             : {
      59             :   /* Make it definitely odd.  */
      60       39754 :   seed |= 1;
      61             : 
      62       79586 :   while (!is_prime (seed))
      63          39 :     seed += 2;
      64             : 
      65       34051 :   return seed;
      66             : }